上海交通大学李听昕团队研究了扭曲双层MoTe₂第二莫尔带拓扑结构与相关性之间的相互作用。该研究于2025年3月20日发表在《自然—物理学》杂志上。

二维晶格系统中形成的拓扑平带为在没有外部磁场的情况下研究物质的分数相提供了机会。例子包括分数量子反常霍尔效应和分数拓扑绝缘体。最近，在六方氮化硼上的扭曲双层MoTe₂和菱面体堆叠多层石墨烯中，实验实现了分数量子反常霍尔效应。这些研究主要集中在第一莫尔平带上，但有可能在第二莫尔带中出现非阿贝尔态。

研究组对扭曲双层MoTe₂器件进行了系统的输运研究，重点研究了第二莫尔带。结果观察到第二莫尔带中的铁磁性，以及由平面外磁场驱动的Chern绝缘体态，每个莫尔晶胞填充三个孔。在每个莫尔晶胞填充2.2到2.7个孔之间，研究组观察到在低温下具有1/T标度定律的有限温度电阻率最小值和较大的平面外负磁阻。施加平面外电场可以在整数和分数填充因子下诱导量子相变。该研究为实现基于扭曲MoTe₂的第一个莫尔平带之外的可调拓扑状态和其他意想不到的磁相奠定了基础。

附：英文原文

Title: Interplay between topology and correlations in the second moiré band of twisted bilayer MoTe2

Author: Xu, Fan, Chang, Xumin, Xiao, Jiayong, Zhang, Yixin, Liu, Feng, Sun, Zheng, Mao, Ning, Peshcherenko, Nikolai, Li, Jiayi, Watanabe, Kenji, Taniguchi, Takashi, Tong, Bingbing, Lu, Li, Jia, Jinfeng, Qian, Dong, Shi, Zhiwen, Zhang, Yang, Liu, Xiaoxue, Jiang, Shengwei, Li, Tingxin

Issue&Volume: 2025-03-20

Abstract: Topological flat bands formed in two-dimensional lattice systems offer an opportunity to study fractional phases of matter in the absence of an external magnetic field. Examples include fractional quantum anomalous Hall effects and fractional topological insulators. Recently, fractional quantum anomalous Hall effects have been experimentally realized in both twisted bilayer MoTe2 and rhombohedral-stacked multilayer graphene on hexagonal boron nitride. These studies focus mainly on the first moiré flat band, but there is a possibility that non-Abelian states could occur in the second moiré band. Here we present a systematic transport study of twisted bilayer MoTe2 devices, focusing on the second moiré band. We observe ferromagnetism in the second moiré band, and a Chern insulator state driven by out-of-plane magnetic fields at a filling factor of three holes per moiré unit cell. Between fillings of 2.2 and 2.7 holes per moiré unit cell, we observe a finite temperature resistivity minimum with a 1/T scaling law at low temperatures and a large out-of-plane negative magnetoresistance. Applying an out-of-plane electric field can induce quantum phase transitions at both integer and fractional filling factors. Our studies lay the groundwork for realizing tunable topological states and other unexpected magnetic phases beyond the first moiré flat band based in twisted MoTe2.

DOI: 10.1038/s41567-025-02803-1

Source: https://www.nature.com/articles/s41567-025-02803-1